Battery run time for different terrains .

i want to manufacture a trike which is human powered as well as motor operated ...... for this i am using a 400 watts pmdc motor of 1500 rpm ..two batteries of 12 v and 26 Ah each, the total weight of my vehicle would be 350 kg.is it feasible ?how to calculate battrey run time for different terrains ???? please reply......

Yes, it will work because you are enthusiastic, but it may only crawl slowly up hills.
There will be losses. If you design very well you may get to 80% efficiency.
I would consider adding a couple of 200 watt solar panels as a sunshade.

You may need to gear down the motor a bit to drive your chosen wheel diameter. The selection of gear ratio will depend on the steepest hill you will need to climb.

By using two motors, you can switch them easily from series to parallel. In series they will run at half the speed of the parallel connection. In series they will have equal torque.

Will you use regenerative braking? That will increase your range in undulating hill country or in stop-start traffic.

You will get best range if you can PWM the motor drive as that will give you better economy at varying speeds. It will match the voltage of your supply to the voltage required by the motor at any particular speed. That is the electrical equivalent of the torque converter in an automatic gearbox.

There are too many unknowns in your question to calculate range.
But there are three things that can be calculated on electric power alone, ignoring losses.

Thirdly; You can use those results to give you the time it will take to flatten both batteries.
654.9 / 0.116 = 5645 seconds = 1.568 hours.
Note: that this is the same as ( 2 * 12V * 26Ah ) / 400W = 1.56 hours